I hadn't realized that the standard higher order sequence functions compose in a manner
that requires quite a bit of run-time machinery. For example nested map calls will cause
a separate lazy sequence to be instantiated at each level of nesting, with each level
"pulling" results from the next innermost as needed. The function calls are thus temporally
interleaved, but the functions are not actually composed. We can see this happening by
adding some printlns to some unary functions and then running a nested …

Mr Podsnap was well to do, and stood very high in Mr Podsnap's opinion.
Beginning with a good inheritance, he had married a good inheritance,
and had thriven exceedingly in the Marine Insurance way, and was
quite satisfied. He never could make out why everybody was not quite
satisfied, and he felt conscious that he set a brilliant social example
in being particularly well satisfied with most things, and, above all
other things, with himself.

Thus happily acquainted with his own merit and importance, Mr Podsnap
settled that whatever he put behind him he put out of existence. There
was …